Process for the production of cellulosic material



Patented Aug. 27, 1929.

CARL LEYST, QF BERLIN,

GERMANY, ASSIGNOR F ONE-HALF TO ARTHUR HENRY LYMN, OF LONDON, ENGLAND.

rnoonss roe THE rnonnorron OF oELLuLosIc MATERIAL.

No Drawing. Application filed November 11, 1926, Serial No. 147,849, and in Great Britain This invention relates to a process for the production of cellulosic materiaL,

Cellulose pulp is at present generally pro-.

duced from wood, by one of three methods'viz, by the soda process, the sulphite process or by electric means, and from straw or grass such as esparto by the soda process only.

According tothe soda process the wood, straw or grass is cut up into suitable size and digested or boiled, strong alkali such as caustic soda liquor being run into the digester with the disintegrated raw material and cooked or boiled by the admission of steam for removing the incrustating substance from the fibrous material.

After the boiling is complete the mixture of pulp and liquor is discharged into washing tanks where it is drained and freed from that coloured liquor the latter being evaporated and treated for recovering the soda contained in it. I l

The washed pulp is thereafter screened thickened and bleached or otherwise treated.

Now bamboo is a well known fibrous material which,-if it could be treated economically, would be very suitable for the manufacture' of cellulose pulp. However on account of the geographical situation of .its growth this valuable material has not hitherto been successfully commercially used for the production of cellulose.

It has already been proposed to boil crushed bamboo with water containing 525% lime, in order to obtain a paper makers half stuff,

but such a product is relatively voluminous and diflicultly transportable, and so far as I am aware it has never been suggested to press the half stufl'. alleged to be obtained into a form suitable for cheap and economical trans- 40 port.

The present invention however provides a simple and economical process for producing from bamboo an excellent cellulosic material adapted to be worked up into paper .or the like with a minimum additionalexpense, which process com; rises finely disintegrating the bamboo, pre erably by cutting the stemsv into pieces of a thickness of about. one to five millimetres, boiling with quicklime until the material can be worked -up to a pulp and after washing the material thus obtained, forming it into cakes byvsubmitting it to a moderate pressure which is adequate so that 'onsub- November sequent drying the cakes have obtained enough coherence to be transported. The pulp cakes thus obtained can be further worked for example ground and treated with caustic soda of a low concentration when it is desired to convert the same into finished pulp, paper or the like. 7

In order to carry out the process successfully it is es'sentialthat the bamboo should be adequately disintegrated, as without this fine disintegration the subsequent action of the quicklime which softens the individual disintegrated particles so that they can be transformed into cake form, cannot be effected satisfactorily.

The limeboiling is carried out with about 35% by weight of quickdime (based upon the dry bamboo material) in adequate water at a temperature of 95 to 100 0., and onlyfor such a time until the material can be worked up to a pulp. This time is generally about ten hours, The lye is then removed and after" 75' washing the pulp is milled with water.

The material thus obtained is .then pressed into cakes which can be efiected by hydraulic, mechanical or other means. The pressure for transforming the milled material into cakes should be just suflicient to cause the cohesion of the cakes on subsequent drying. Any high pressure must be avoided because the sub- "sequent disintegration of the cakes for further working up would be made too difficult.

The half stuff which has'been obtained in this manner can be properly disincrustated by subsequent treatment with caustic soda of low concentration.

The pressed cakes of the present invention take up comparatively small space which is a decided advantage in practice because the further working up of the bamboo pulp cakes can be eiiected at a place far away from the place where the material has been produced, without necessitating excessive costs for transport. The present invention provides the further/advantage that the after-treat ment with caustic alkali required to convert the pulp cakes into. finished pulp, paper or the like can be effected with caustic soda of lower concentration than that usually required in paper manufacturing processes.

In order to understand the invention more clearly reference is made to the following working example a The bamboo stems, about the thickness of an arm, from which the leaves have been removed, are cut to pieces on a sawing'table and the knots removed. The internodal portions are placed in a squeezing press where they are sliced up and are thereupon disintegrated in a devilling machine, after which the material falls upon a transporter belt and is transferred by an elevator into a sile or boiler, preferably of the revolving type.

The bamboo, disintegrated to pieces of about 1 to 5 millimetres thickness and about to millimetres length, is introduced into a spherical iron boiler with about by weight of quick-lime based upon the dry bambo0 material and three times the amount of water and is heated by direct contact with steam to a temperature of 95 to 100 C., at

which itis maintained for about ten hours.

The lime is added in the form of milk of lime through a sieve of about 2' millimetres mesh adapted to retain as much as possibleof the sandy residues. Every hour the boiler is revolved for about ten minutes in order to obtain a uniformlyboiled product.

-' After the l-oiling has terminated, the lye is transferred to another boiler filledwith bamboo. This procedure however cannot be repeated indefinitely as otherwise the colour and adaptability to bleaching of the final product is interfered with. After the rcmoval of the lye, the boiler is filled with water two or three times and revolved and the Water is discharged in order to wash out as much lime as possible from the boiled material. Finally the boiler is emptied and the bamboo, although freed only to aslight extent from its :incrustations but loosened in structure and still containing about 60% moisture, is ground in a mill with. addition of. sufficient amountsof. water until cake-forn'iability has been attained (90 t6 120 minutes) or until the chips have been opened up into fibres, which takes about 3 to l hours. The mass thus obtained which contains 7 5 to 80% water ,is pressed in a spindle press or hydraulic press with just sufiicient pressure to cause coherence of the cakes when dried. After pressing, the cake, still contains 50% water and has a fibre content of about 250 grs. per cubic deem. The cake thus obtained may either be air dried or dried in a drying tunnel at 50 to (1., whereby the fibre content is increased to 300 grms. per cubic deem.

If the ground material is washed in known manner, prior to pressing, that is to-say agitated with water and passed over a longitudinal sieve. the fibre content increases per unit volume from 15 to 18%.

In. order to refine the material for the production of fine paper pulp or paper, the cakes are broken down and treated in the usual manner but with less than usual viz. 6 to 9% of caustic soda, (calculated on the dry bamboo material) in solution of adequate concentration. This treatment is carried out for about 4 hours at 2 atmospheres pressure and may be effected in the same spherical boilers in which the boiling with lime has been carried out. After the boiling'is completed, the pressure is reduced, the waste lye removed, and the material left behind is conveyed to the bleaching apparatus. There it is concentrated and slowly (according to the degree of whiteness required) bleached by means of bleaching liquor of adequate concentration but containing 25 to 50% chloride of lime (mileulated on the dry material) at 40 C. After the bleaching, the bleaching liquor is removed from the material which is again washed and thereupon worked on a cellulose pulp machine in the 'usualmanner.

It has been found that when working with this process the following yields can be obtained By boiling the bamboo with lime the loss in the treatment lies between 6 and 8% andcrushing entails a further loss of 9 to 10%. Thus in obtaining bamboo cake material. a yield of about to% can be expected. As previously stated the'material may be improved by treating with caustic soda solution in order to render it easier to bleach. If this is done a loss of 16 to 20% occurs, so that a yield of only 60% is attained.

Bleaching the material entails a further loss of 5 to 15% according to the degree. of bleaching. The yield of the improved and bleached material would then be about 45 to 50% of the original bamboo.

I claim 1. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo with quick-lime to form a pulp, washing said pulp and rendering same coherent by compression.

2. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo with quick-lime to form a pulp, washing said pulp, grinding the washed pulp and rendering same coherent by compression.

3. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises comminuting bamboo stems into pieces of an approximate thickness of about 1 to 5 millimetres. and suitable length, boiling the disintegrated bamboo with quick-lime to form a pulp, mashing said pulp and rendering same coherent by compression.

4. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises comminuting a sion.

5. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises cutting 'up bamboo stems into-pieces of an approximate 10 thickness-of about 1 to 5 millimetres and suitable length, treating the "out bamboo stems with about 35% by Weight of quicklime (based upon the dry bamboo material) in adequate water, at, a temperature of 95 to 100 0., for about ten hours, removing the lye and washing the lime from the boiled material, thereupon treating the pulp thus obtained in a potcher with water for one and a'half to two hours, submitting the mass thus obtained to sufficient pressure to form cakes and drying said cakes.

6. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo with quick-lime to form a pulp, washing said pulp, rendering same coherent by compression and treating said compressed material with soda lye.

7. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo with quick-lime to form a pulp, washing said pulp, grinding the washed pulp, renderingv the ground" material coherent by compression and treating said compressed material with soda lye.

8. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises comminuting bamboo stems into pieces of an approximate thickness of about 1 to 5 millimetres and suitable length, boiling the disintegrated cellulosic material suitable for use in paper manufacture, which comprises cutting up bamboo stems into pieces of an approximate thickness of about 1 to 5 millimetres and suitable length, treating the cut bamboo with soda lye.

stems'witli about 35% by weight of quicklime (based upon the dry bamboo material) in adequate water, at a temperature of 95 to 100 0., for aboutte'n hours, removing the lye'and washing the lime from the boiled material, thereupon treating the pulp thus obtained 'inafpotcher with water for one and a half to two hours, submitting the mass thus obtained to: suflicient pressure to form cakes, dryingsaid cakes and treating same 11. The process? for the roduction of a cellulosic material suitable oruse in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo with quick-lime to form a pulp, washing said pulp, rendering same coherent by compression, treating the compressed material with about 6 to 9% caustic soda (calculated on the dry material) in suitablesolution in a boiler for about four hours at a pressure of about 2 atmospheres, removin the lye and washing the treated materia with water, thereupon concentrating the pulp and treating same with 25'to 50% chl0- ride of lime (calculated on the dry material) in adequate water at 40 (1., finally washing the bleached material and working same on a cellulose pulp machine.

12. The process for the roduction of a cellulosicfimaterial suitable or use in paper manufacture, which comprises finely disintegrating bamboo, boiling the disintegrated bamboo .with quick-lime to form a pulp, washing said pulp, grinding the washed pulp, rendering the ground material coherent by compressiom'treating the compressed material with about 6 to 9% caustic soda (calculated on the dry material) in suitable solution in a boiler for about four hours at a pressure of about 2 atmospheres, removing the lye and washing the treated material with water, thereupon concentrating the pulp and treating samewith 25 to 50% chloride of lime (calculated on the dry material) in adequate water at40 0., finally washing the bleached material and working same on a cellulose pulp machine.v

13. The process for the production of a cellulosic material suitable for use in paper manufacture, which comprises comminuting bamboo stems into pieces of an approximate thickness of about. 1 to 5 millimetres and suitable length, boiling the disintegrated ing same with 25 to 50% c loride of lime (calculated on the dry material) in adequate water at 40 C., finally washing the bleached material and working same on a cellulose pulp machine.

14. The. procesf sf for the production of a cellulosic material suitable for use in paper manufacture, which comprises cutting up bamboo stems .into pieces of an approximate thickness of about 1 to 5 millimetres and suitable length, treating the cut bamboo steins with about 35% by Weight of quick-lime (based upon the dry bamboo material) in adequate. water, at a temperature of 95 to 100 (3., for about ten hours, removing the lye and washing the lime from the boiledmaa half to two hours and finally submitting the mass thus obtained to suflicient pressure to form cakes and drying said cakes, treating said cakes with about 6 to 9% caustic soda (calculated on the dry material) in suitable solution in a boilerfor about four hours at a pressure of about 2 atmospheres,-removing the lye and washing the treated material with water, thereuponponcentrating the pulp and treating same with '25 to 50% chloride of lime (calculated on the dry material) in adequate water at 40 C., finally washing the bleached material and "working same on a cellulose pulp machine.

' In testimony whereof, I

' CARL LEYST.

afiix my signature. 

